Estivation is one of nature’s most remarkable survival strategies. While most people are familiar with hibernation, fewer know about its hot-weather counterpart. Estivation (sometimes spelled aestivation) is a state of dormancy or deep sleep that helps animals survive extreme heat or drought. During this period, their metabolism slows, their movement nearly stops, and they wait out the harsh conditions until the environment becomes livable again. From amphibians buried in the mud to snails sealed in their shells, here are some fascinating animals that estivate and how they do it.
African Lungfish
The African lungfish is one of the best-known examples of an animal that estivate. Found in parts of Africa where ponds and rivers dry up during the dry season, this fish has evolved an incredible way to survive without water for months.
When the heat sets in, it burrows into the mud and secretes mucus that hardens into a protective cocoon, leaving only a small hole for breathing.
Desert Snails
Desert snails are experts at estivation, using it to endure long stretches of intense heat and dryness. When temperatures rise and humidity drops, they retreat into their shells and seal the opening with a layer of dried mucus called an epiphragm.
This barrier prevents water loss and helps them retain moisture. Some snails can remain in this state for several years, waiting patiently for rain to return. When moisture levels rise again, they rehydrate and come back to life almost instantly.
Crocodiles
Crocodiles, particularly those living in parts of Africa and Australia, are known to estivate during long dry seasons. When rivers and swamps dry up, they dig burrows in the mud or find shaded areas to rest. Their activity level drops significantly, and their metabolism slows down, allowing them to survive for months with very little food or water.
African Bullfrog
The African bullfrog, one of the largest frog species in the world, spends much of its life underground. When the rainy season ends and the water evaporates, this frog burrows deep into the soil and secretes a mucus layer that hardens into a cocoon. Inside, it can survive up to a year without food or water.
Lungless Salamanders
Some species of lungless salamanders, especially those living in regions that experience seasonal dryness, enter estivation to avoid dehydration. They find cool, moist hiding spots under rocks, logs, or underground burrows and remain there until conditions improve. During estivation, their heart rate and breathing slow dramatically, allowing them to conserve energy and water.
Earthworms
Earthworms are known for thriving in moist soil, but when drought hits, they go underground—literally. They dig deep into the soil where there’s still some moisture and curl up into tight balls to reduce water loss. Their metabolic processes slow down significantly during estivation.
Common Box Turtle
The common box turtle, native to North America, has an interesting adaptation to both cold and heat. It hibernates in winter and estivate in extreme summer conditions. During estivation, it burrows into the ground or hides under leaf litter to escape the high temperatures and avoid dehydration.
Spadefoot Toads
Spadefoot toads, found in deserts and semi-arid regions, have one of the most efficient estivating systems among amphibians. They spend most of the year buried underground, emerging only during heavy rains to breed in temporary pools.
Once breeding is done, they return to the soil and remain in estivation until the next rainy season. Their bodies are specially adapted to minimize water loss, and their metabolism can remain slow for nearly a year.
Land Crabs
In certain tropical regions, some species of land crabs enter estivation during dry seasons to survive high heat and low humidity. They dig deep burrows or retreat into moist crevices to reduce water loss. During this time, their activity drops significantly, and they live off stored fat reserves. Once the rains return, they emerge in large numbers, often migrating toward the ocean to reproduce.
Lemurs
The fat-tailed dwarf lemur of Madagascar is one of the few primates known to undergo estivation. It stores fat in its tail during the wet season, which it then uses as energy during the dry season. When food becomes scarce, the lemur retreats into tree holes and enters a state of dormancy. Its body temperature and metabolism drop dramatically, allowing it to survive the harsh, food-scarce months until conditions improve.
Giant African Land Snail
Another remarkable estivator is the giant African land snail. During the dry season, it retreats into its shell and seals the opening with a layer of mucus, much like other snail species. In this state, it can survive for several months without water. Once humidity levels rise, the snail reawakens, becoming active again to feed and reproduce.
Why Do Animals Estivate?
The main reason animals estivate is to conserve energy and water in harsh environments. By slowing down their metabolism, they minimize the amount of oxygen, food, and water they need to survive. This adaptation is especially useful in regions with unpredictable climates, where long dry spells can make survival difficult for creatures that depend on moisture.
How Long Can Animals Estivate?
The length of estivation varies widely between species. Some animals, like frogs and snails, may estivate for just a few weeks until rain returns. Others, such as the African lungfish, can remain in estivation for several years if drought conditions persist.
What’s even more impressive is that many of these animals can quickly return to normal activity once the environment improves, with no lasting damage to their bodies.
